Nitrates in processed meats and botulism

Nitrates or not? Surely another issue that needs a proper risk assessment

Over the festive period there has been a lot of press reporting various individuals applying pressure to the meat industry to remove nitrates from processed meat products. Headlines have appeared such as this “’Vast majority of bacon contains cancer-causing chemicals, say campaigners urging the Government to take action on nitrates in processed meats” (https://www.dailymail.co.uk/news/article-6538803/Call-action-cancer-risk-processed-meats-like-bacon-ham.html ). Indeed, this issue has been swirling around at least since I was an undergraduate in the late 1970s, and it is claimed that there is mounting evidence that nitrate is not a particularly desirable chemical to be present in food, despite the fact that it occurs naturally in many foods considered to be healthy such as leafy green vegetables.

However, there is a reason for nitrate to be present in meat products, and that is because it controls very nicely the growth and toxin production by Clostridium botulinum. In fact, the word botulinum comes from the latin word for sausage, botulus, because, in their day, intoxications and deaths caused by the organism were associated with the consumption of sausages, especially blood sausages eaten in continental Europe.

Some background is given on the history of botulism on this website: https://www.meatsandsausages.com/sausage-making/meat-safety/botulism although it cannot be taken as an objective source. Further information can be obtained from older texts published closer to times when botulism was more of a problem. I have a book, “Food Poisoning” by Dack, G.M. published in 1943 by Chicago University Press that contains a chapter on botulism. It reports that the first case was described in 1753 and lists outbreaks in the USA involving meat products including ham, sausage, beef and a variety of other products. Being an American book most of the focus was on home canned foods. My “Manual of Bacteriology” by Muir, R and Ritchie J., which was published in 1907, describes the isolation of ‘bacillus botulinus’ from ham “the ingestion of which in the raw condition had produced a number of cases of poisoning, some of them followed by a fatal result” (p 394). Erbguth (2007) gives a detailed account of the early history of botulinum intoxications, describing the collation of hundreds of case reports by Justinus Kerber who was a German physician. It also recounts the outbreak in Belgium involving 34 cases who had eaten the ham mentioned above. Of these three people died.

However, the incidence of disease is not clear was since the rigorous investigation of foodborne disease outbreaks which would be usual today were simply not possible. Clearly though there was a problem with meat products at the time that needed to be addressed. Concern about the disease led to the use of nitrates in certain meat products starting in the USA in 1925. Similarly, a better understanding of the heat treatment needed to kill spores contributed to the production of acceptably safe canned foods. Effectively botulism became controlled with outbreaks largely confined to foods produced domestically or where failures of processing had occurred. Interestingly botulism occurs from time to time following the consumption of unexpected foods such as baked potatoes, mascarpone cheese and pickled eggs.

The absence of intoxications and death from botulism in modern times in the UK indicates that controls and food regulations are working, so caution needs to be observed before changing those mitigating factors. Do we think that spores of the organism are no longer as common as they used to be and so pose reduced risk? If nitrate were to be removed from food then does this then also mean that the ‘10 day rule’ (https://www.chilledfood.org/the-10-day-rule-for-shelf-life/ ) for foods should be abandoned as we would no longer be worried about C. botulinum and can ignore it as a hazard needing control in foods?

I personally don’t know the answer to these questions as the pros and cons of the inclusion of nitrates in meat products do not seem, to my knowledge, to have been assessed on an objective and quantitative basis. The available evidence does not seem to be consistent or, at least, is nuanced (e.g. https://www.efsa.europa.eu/sites/default/files/corporate_publications/files/nitrates-nitrites-170614.pdf; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4690057/  ).Further rigorous risk assessment examining both sides of the coin needs to happen in my view.

A control option is to formulate processed meat products in such a way that the pathogen cannot grow when nitrates are not included in the recipe. The critics of the use of nitrates refer to meat products where this seems to have been successfully achieved, but what works for one product is unlikely to work for them all. The whole area looks ripe for a “hurdle” approach (McIntyre and Hudson, 2009).

REFERENCES

Erbguth, F.J. (2007) From poison to remedy: the chequered history of botulinum toxin. Journal of Neural Transmission

McIntyre, L., and Hudson, J.A. (2009) Something old, something new: Hurdle technology-a marriage of preservation techniques. Food New Zealand 9(1), 15-20).